Clinical validation of a ctDNA-Based Assay for Multi-Cancer Detection: An Interim Report from a Vietnamese Longitudinal Prospective Cohort Study of 2795 Participants.

The SPOT-MAS assay "Screening for the Presence Of Tumor by Methylation And Size" detects the five most common cancers in Vietnam by evaluating circulating tumor DNA in the blood. Here, we validated its performance in a prospective multi-center clinical trial, K-DETEK. Our analysis of 2795 participants from 14 sites across Vietnam demonstrates its ability to detect cancers in asymptomatic individuals with a positive predictive value of 60%, with 83.3% accuracy in detecting tumor location. We present a case report to support further using SPOT-MAS as a complementary method to achieve early cancer detection and provide the opportunity for early treatment.

Is Serum Lactate a Good Predictor of Mortality in Children Aged 2 Months to 5 Years With Pneumonia in Central Vietnam.

Pneumonia is a major cause of morbidity and mortality in children globally. Lactate, a product of anaerobic cellular metabolism, has been used as an indicator of poor tissue oxygenation and cellular hypoxia. Our objective was to determine whether serum lactate concentration at hospital admission predicted mortality in children aged 2 months to 5 years with pneumonia. Two hundred and eighty-one pediatric patients admitted to the Department of Pediatrics of a provincial hospital with WHO-defined pneumonia and severe pneumonia were included; of whom, 8 died during hospital stay. The median serum lactate concentration was 4.8 mmol/l (IQR 2.6-6.9) among children who died and 3.6 mmol/l (IQR 2.8-4.3) among children who survived (P > .05); 4.1 mmol/l (IQR 2.7-4.7) among children with severe pneumonia and 3.5 mmol/l (IQR 2.8-4.3) among children with pneumonia (P > .05). Serum lactate concentration had a low value in predicting pneumonia-related mortality (AUC 0.68, 95% CI 0.62-0.73); and the concentration cut-off of >4.06 mmol/l had the best sensitivity and specificity (75% and 68.9%, respectively) with a 2.4-fold risk of death (LR+ 2.4; 95% CI 1.6-3.7). Although hyperlactatemia was associated with severity and mortality in children 2 months to 5 years of age with pneumonia, its benefit was unclear.

Impact of Amino Acid Substitutions in Region II and Helix K of Herpes Simplex Virus 1 and Human Cytomegalovirus DNA Polymerases on Resistance to Foscarnet.

Amino acid substitutions conferring resistance of herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV) to foscarnet (PFA) are located in the genes UL30 and UL54, respectively, encoding the DNA polymerase (pol). In this study, we analyzed the impact of substitutions located in helix K and region II that are involved in the conformational changes of the DNA pol. Theoretical substitutions were identified by sequences alignment of the helix K and region II of human herpesviruses (susceptible to PFA) and bacteriophages (resistant to PFA) and introduced in viral genomes by recombinant phenotyping. We characterized the susceptibility of HSV-1 and HCMV mutants to PFA. In UL30, the substitutions I619K (helix K), V715S, and A719T (both in region II) increased mean PFA 50% effective concentrations (EC50s) by 2.5-, 5.6-, and 2.0-fold, respectively, compared to the wild type (WT). In UL54, the substitution Q579I (helix K) conferred hypersusceptibility to PFA (0.17-fold change), whereas the substitutions Q697P, V715S, and A719T (all in region II) increased mean PFA EC50s by 3.8-, 2.8- and 2.5-fold, respectively, compared to the WT. These results were confirmed by enzymatic assays using recombinant DNA pol harboring these substitutions. Three-dimensional modeling suggests that substitutions conferring resistance/hypersusceptibility to PFA located in helix K and region II of UL30 and UL54 DNA pol favor an open/closed conformation of these enzymes, resulting in a lower/higher drug affinity for the proteins. Thus, this study shows that both regions of UL30 and UL54 DNA pol are involved in the conformational changes of these proteins and can influence the susceptibility of both viruses to PFA.

Structural insights into the putative bacterial acetylcholinesterase ChoE and its substrate inhibition mechanism.

Mammalian acetylcholinesterase (AChE) is well-studied, being important in both cholinergic brain synapses and the peripheral nervous systems and also a key drug target for many diseases. In contrast, little is known about the structures and molecular mechanism of prokaryotic acetylcholinesterases. We report here the structural and biochemical characterization of ChoE, a putative bacterial acetylcholinesterase from Pseudomonas aeruginosa Analysis of WT and mutant strains indicated that ChoE is indispensable for P. aeruginosa growth with acetylcholine as the sole carbon and nitrogen source. The crystal structure of ChoE at 1.35 Å resolution revealed that this enzyme adopts a typical fold of the SGNH hydrolase family. Although ChoE and eukaryotic AChEs catalyze the same reaction, their overall structures bear no similarities constituting an interesting example of convergent evolution. Among Ser-38, Asp-285, and His-288 of the catalytic triad residues, only Asp-285 was not essential for ChoE activity. Combined with kinetic analyses of WT and mutant proteins, multiple crystal structures of ChoE complexed with substrates, products, or reaction intermediate revealed the structural determinants for substrate recognition, snapshots of the various catalytic steps, and the molecular basis of substrate inhibition at high substrate concentrations. Our results indicate that substrate inhibition in ChoE is due to acetate release being blocked by the binding of a substrate molecule in a nonproductive mode. Because of the distinct overall folds and significant differences of the active site between ChoE and eukaryotic AChEs, these structures will serve as a prototype for other prokaryotic acetylcholinesterases.

Hypersusceptibility of Human Cytomegalovirus to Foscarnet Induced by Mutations in Helices K and P of the Viral DNA Polymerase.

Herein, we phenotypically and enzymatically characterize the theoretical mutation Q579I in helix K and the already described clinical mutation K805Q in helix P of cytomegalovirus DNA polymerase for susceptibility to foscarnet. Q579I and K805Q recombinant viruses were hypersusceptible to foscarnet (respective mean 50% effective concentrations [EC50] of 0.12- and 0.19-fold that of the wild type). Three-dimensional modeling analysis suggested that both mutations favor the closed conformation of the enzyme to which foscarnet binds with a higher affinity.

Compartmentalization of a Multidrug-Resistant Cytomegalovirus UL54 Mutant in a Stem Cell Transplant Recipient with Encephalitis.

We report a case of cytomegalovirus encephalitis in a hematopoietic stem cell transplant recipient. A previously uncharacterized V787E mutation in UL54 was identified in cerebrospinal fluid but not plasma specimens. For the V787E recombinant virus, the half maximal effective concentrations for ganciclovir, foscarnet, and cidofovir were 8.6-, 3.4- and 2.9-fold higher than for wild-type virus, and the replicative capacity was lower. The introduction of a bulkier and negatively charged glutamate residue at position 787 could destabilize the finger domain of UL54 DNA polymerase. Viral genotyping of cerebrospinal fluid is warranted in subjects with cytomegalovirus encephalitis, owing to the low penetration of antivirals in this compartment.

Determination of spontaneous dicentric frequencies and establishment of dose-response curves after expose of human peripheral blood lymphocytes to low- and high-dose rate 60Co gamma rays - the basis for cytogenetic biodosimetry in Vietnam.

PURPOSE: The purposes of this study are to investigate spontaneous dicentric frequencies and dose-response curves of dicentrics induced by gamma 60Co for replenishing the data sets used for biodosimetry in Vietnam. MATERIALS AND METHODS: One hundred and four healthy donor blood samples were collected for chromosome aberrations background study, 03 healthy donor blood samples were used for generating the dose-response curves at 1.96 mGy/min and 275 mGy/min. Blood collection, in vitro irradiation, cell culture and harvest, slide preparation and metaphase scoring were performed according to IAEA standard protocol (2011). Blind exposed samples were scored for verifying each curve. RESULTS: The dicentric, fragment and chromatid break frequencies in 106,310 metaphases of 104 donors were 0.023% ± 0.005%, 0.045% ± 0.007% and 0.101% ± 0.011%, respectively. The dose-response curve for low-dose rate was y = C + (0.0137 ± 0.0055)D + (0.0912 ± 0.0142)D2 and for high-dose rate was y = C + (0.0337 ± 0.0046)D + (0.0539 ± 0.0031)D2, where both of them were verified. CONCLUSION: The data of this study were established for biological dose assessment in cases with low LET of accidental or occupational radiation exposures in the dose range of 0.1-5.0 Gy.

Co-Localization of GABA Shunt Enzymes for the Efficient Production of Gamma-Aminobutyric Acid via GABA Shunt Pathway in Escherichia coli.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid, which is an important inhibitor of neurotransmission in the human brain. GABA is also used as the precursor of biopolymer Nylon-4 production. In this study, the carbon flux from the tricarboxylic acid cycle was directed to the GABA shunt pathway for the production of GABA from glucose. The GABA shunt enzymes succinate-semialdehyde dehydrogenase (GabD) and GABA aminotransferase (GabT) were co-localized along with the GABA transporter (GadC) by using a synthetic scaffold complex. The co-localized enzyme scaffold complex produced 0.71 g/l of GABA from 10 g/l of glucose. Inactivation of competing metabolic pathways in mutant E. coli strains XBM1 and XBM6 increased GABA production 13% to reach 0.80 g/l GABA by the enzymes co-localized and expressed in the mutant strains. The recombinant E. coli system developed in this study demonstrated the possibility of the pathway of the GABA shunt as a novel GABA production pathway.

Engineering the intracellular metabolism of Escherichia coli to produce gamma-aminobutyric acid by co-localization of GABA shunt enzymes.

OBJECTIVES: To direct the carbon flux from Krebs cycle into the gamma-aminobutyric acid (GABA) shunt pathway for the production of GABA by protein scaffold introduction in Escherichia coli. RESULTS: Escherichia coli was engineered to produce GABA from glucose by the co-localization of enzymes succinate semialdehyde dehydrogenase (GadD), GABA aminotransferase (PuuE) and GABA transporter (GadC) by protein scaffold. 0.7 g GABA l(-1) was produced from 10 g glucose l(-1) while no GABA was produced in wild type E. coli. pH 6 and 30 °C were optimum for GABA production, and GABA concentration increased to 1.12 g GABA l(-1) when 20 g glucose l(-1) was used. When competing metabolic networks were inactivated, GABA increased by 24 % (0.87 g GABA l(-1)). CONCLUSIONS: The novel GABA production system was constructed by co-localization of GABA shunt enzymes.

Redirection of Metabolic Flux into Novel Gamma-Aminobutyric Acid Production Pathway by Introduction of Synthetic Scaffolds Strategy in Escherichia Coli.

In general, gamma-aminobutyric acid (GABA) pathway involves the decarboxylation of glutamate, which is produced from sugar by Corynebacterium fermentation. GABA can be used for the production of pharmaceuticals and functional foods. Due to the increasing demand of GABA, it is essential to create an effective alternative pathway for the GABA production. In this study, Escherichia coli were engineered to produce GABA from glucose via GABA shunt, which consists of succinate dehydrogenase, succinate-semialdehyde dehydrogenase, and GABA aminotransferase. The three enzymes were physically attached to each other through a synthetic scaffold, and the Krebs cycle flux was redirected to the GABA pathway. By introduction of synthetic scaffold, 0.75 g/l of GABA was produced from 10 g/l of glucose at 30 °C and pH 6.5. The inactivation of competing metabolic pathways provided 15.4 % increase in the final GABA concentration.

Production of gamma-aminobutyric acid from glucose by introduction of synthetic scaffolds between isocitrate dehydrogenase, glutamate synthase and glutamate decarboxylase in recombinant Escherichia coli.

Escherichia coli were engineered for the direct production of gamma-aminobutyric acid from glucose by introduction of synthetic protein scaffold. In this study, three enzymes consisting GABA pathway (isocitrate dehydrogenase, glutamate synthase and glutamate decarboxylase) were connected via synthetic protein scaffold. By introduction of scaffold, 0.92g/L of GABA was produced from 10g/L of glucose while no GABA was produced in wild type E. coli. The optimum pH and temperature for GABA production were 4.5 and 30°C, respectively. When competing metabolic network was inactivated by knockout mutation, maximum GABA concentration of 1.3g/L was obtained from 10g/L glucose. The recombinant E. coli strain which produces GABA directly from glucose was successfully constructed by introduction of protein scaffold.

Modification of response behavior of zinc sensing HydHG two-component system using a self-activation loop and genomic integration.

Characterizing the dynamics of HydHG-a two-component transcriptional regulatory network for exogenous zinc in E. coli-is essential in understanding the biology of these regulatory and signaling pathways. Here, we used a synthetic biology strategy to modify the dynamic characteristics of the HydHG network in two ways. First, a self-activation loop for HydHG network was created under the control of zraP promoter, after which the threshold Zn(2+) concentration for the self-activated HydHG network significantly decreased from 200 to 10 µM. Second, the self-activation loop was integrated into the E. coli genome allowing the threshold Zn(2+) concentration to be elevated to 500 µM. As the threshold Zn(2+) concentration could be modified in both directions, the introduction of a self-activation loop and the entire genomic integration strategy may prove useful for the creation of a two-component bacterial biosensor with varying sensitivities.

Modification of CusSR bacterial two-component systems by the introduction of an inducible positive feedback loop.

The CusSR two-component system (TCS) is a copper-sensing apparatus of E. coli that is responsible for regulating the copper-related homeostatic system. The dynamic characteristics of the CusSR network were modified by the introduction of a positive feedback loop. To construct the feedback loop, the CusR, which is activated by the cusC promoter, was cloned downstream of the cusC promoter and reporter protein. The feedback loop system, once activated by environmental copper, triggers the activation of the cusC promoter, which results in the amplification of a reporter protein and CusR expression. The threshold copper concentration for the activation of the modified CusSR TCS network was lowered from 2,476.5 µg/l to 247.7 µg/l, which indicates a tenfold increase in sensitivity. The intensity of the output signal was increased twofold, and was maintained for 16 h. The strategy proposed in this study can also be applied to modify the dynamic characteristics of other TCSs.